Adenosine & caffeine??

[brookesbuddy]

So, I know that caffeine inhibits adenosine's effect during an adenosine nuclear stress test and that patients should avoid caffeine for 12 hours prior to the test. But WHY? Anyone know the pharmacology/physiology behind this?

[CritterLover, BSN, RN]

wow, i'm digging into the long-time-ago memory here, but:

it is believed that caffeine blocks the adenosine receptors (reversable blockade).

it is also believed that caffeine inhibits cyclic nucleotide phosphodiesterase, causing a build up of camp (cyclic adenosine monophosphate).

those both come straight out of my pharm text; i remember #2 being discussed in class in detail.

[mrod, LPN, LVN]

The pharmacological effects of adenosine are blunted in individuals who are taking methylxanthines, ie: caffeine and theophylline because caffeine's stimulatory effects are primarily,although not entirely, credited to its inhibition of adenosine by binding to the same receptors. By nature of caffeine's purine structure it binds to some of the same receptors as adenosine, effectively blocking adenosine receptors in the central nervous system. This reduction in adenosine activity leads to increased activity of the neurotransmitter dopamine.

[anonymurse]

mrod, your post got me wondering about caffiene and gout, and I googled this up: http://www.watercure2.org/caffiene.htm -- as a lifetime caffiene addict, I'd never much thought about its potential adverse effects (though for some reason of its own, my body has gravitated away from coffee and cola to root beer on 7p-7a, and I'm starting to trust my body).

[mrod, LPN, LVN]

Thanks for the website...pretty interesting